In a turbomachine, such as a gas turbine engine, air is pressurized in a compressor then mixed with fuel and burned in a combustor to generate hot combustion gases. The hot combustion gases are expanded within a turbine section including a turbine assembly where energy is extracted to power the compressor and to produce useful work, such as powering a generator to produce electricity. The hot combustion gas travels through a series of turbine stages. A turbine stage may include a row of stationary vanes followed by a row of rotating turbine blades, where the turbine blades extract energy from the hot combustion gas for powering the compressor and may provide output power. The combustion gases are exhausted through a gas path located within a turbine exhaust casing of the turbine assembly.
Components in the turbine assembly require thermal protection to maintain and extend component life, such as may be provided by cooling systems designed into and around the components and/or the use of expensive alloys that are resistant to higher temperatures. Typically, the cooling systems draw cooling air from the compressor, i.e., bleed air, which can decrease the overall efficiency of the engine.